1. Field of the Invention
The present invention relates to a sheet post-processing apparatus and an image forming apparatus, and more particularly to a sheet post-processing apparatus for performing post-processing, such as formation of a fold line, on a sheet having an image formed thereon.
2. Description of the Related Art
Some sheet post-processing apparatuses provided in image forming apparatuses perform post-processing, such as formation of a fold line, on a sheet having an image formed thereon. The reason why the fold line is formed in the sheet includes the following: (1) The sheet is made easy to be folded in a folding step. (2) Bulging of a folded portion of a saddle-stitched brochure is suppressed. (3) The saddle-stitched brochure is made easy to be opened To form a fold line in a sheet, a so-called scoring apparatus as an example of the sheet post-processing apparatus is employed.
To make a saddle-stitched brochure with less opening by suppressing bulging of a folded portion of the saddle-stitched brochure, there has been proposed a scoring apparatus that scores sheets one by one. In this sheet post-processing apparatus, the scored sheets are stacked on a stacking section, and then a sheet bundle of the stacked sheets is saddle-stitched by a stapler and is folded by a folding roller (see Japanese Patent Laid-Open Publication No. 2008-105316).
By the way, it is difficult to accurately score a sheet during conveyance thereof. Therefore, to accurately score the sheet, it is required to stop conveyance of the sheet once and then score the same.
However, to perform scoring of sheets one by one, as described in Japanese Patent Laid-Open Publication No. 2008-105316, it is impossible, before the scoring of one sheet is completed, to convey a next sheet to the scoring apparatus.
Therefore, when scoring is performed, conveyance of each sheet is once stopped, which causes reduction of productivity of the entire processing.